Messaging app WhatsApp filed a lawsuit against Israel-based technology company NSO Group, accusing it of using malware to conduct surveillance on a select group of users.

Specifically, the company alleged NSO Group sent spyware to 1,400 WhatsApp users, which allowed it to access messages and other communications once those missives were decrypted on the user’s device.

WhatsApp head Will Cathcart wrote in an op-ed for the Washington Post the attacks followed a “disturbing pattern,” targeting attorneys, journalists, human rights activists, political dissidents, diplomats and other senior foreign government officials. Users with phone number country codes from the Kingdom of Bahrain, the United Arab Emirates and Mexico were among those impacted.

The company said it detected and halted the suspect activity in May. It added it was able to tie the attacks to NSO Group after an investigation found the originating IP of one of the servers distributing malware was previously associated with the Israeli company. University of Toronto research division Citizen Lab aided WhatsApp in its investigation.

John Scott-Railton, a senior researcher at Citizen Lab, told Ars Technica the lawsuit sets a precedent in attempting to hold the unfettered commercial spyware industry accountable.

However, NSO Group contested the allegations “in the strongest possible terms” in a statement to media, arguing its technology helps government agencies “fight terrorism and serious crime” and is not intended for use against human rights activists and journalists.